Variable inductor



March 30, 1954 G. rs.y MoRToN ETAL VARIABLE INDUCTOR 2 Sheets-Sheet l Filed March 16, 1951 VARIABLE INDUCTOR 2 Sheets-Sheet 2 Filed March 1e, 1951 P www mm M. ,H .M V .5 mi v A e ,qv m f 4 .W QQ 6M W l \L.\ v/uwrv //\///w////////////////\///////////V////////////////////4 ,a m w N uw I w Q www uw www. Nw .m LQ mfr/l5 ,Milf/ffii if fm l wmww w. NNN. l I il Patented Mar. 30, 1954 VARIABLE INDUCTOR George E. Morton, North Royalton, and Maurice F. Baddour, Cleveland, Ohio, assignors to DesignersA for Industry, Inc., Cleveland, lOhio, a

corporation of Ohio Application March 16, 1951, Serial N0. 216,006 4 Claims. (Cl. 336-136) This invention relates to variable inducto-rs and, more particularly, to variable inductors of the kind having a movable core member and adapted for use in the circuits of radio apparatus and the like.

An object of the present invention is to provide an improved variable inductor of the movable core type which is of a very simple and economical construction comprising a minimum number of parts and embodying a novel actuating means for the movable core member.

Another object is to provide an improved vari- Aable inductor of the character mentioned in which the actuating means converts rotary actuating movement into a rectilinear movement of the core member in such a manner as to permit accurate increments of movement for the core member, even though the increments of core movement may be very small.

A further object is to provide a variable inductor of the kind referred to above in which cooperating slot and follower means is employed to produce the desired rectilinear movement of the core member.

Yet another object is to provide a variable inductor of the character mentioned in which the core member comprises connected sections formed of different materials and which sections are movable in succession to an effective position relative to a coil means for producing different desired inductance values.

The invention can be further briefly summarized as consisting in certain novel combinations and arrangements of parts hereinafter described and particularly set out in the claims hereof.

In the accompanying sheets of drawings,

Fig. 1 is a front elevation of a variable inductor embodying the present invention;

Fig. 2 is a longitudinal section taken through the variable inductor on .section line' 2-2 of Fig. 1; l

Fig. 3 is a transverse section taken through the variable inductor on section. line 3-3 of Fe.2; ,.1 L

Fig. 4 is an elevation showing the rotary driving sleeve in detached relation; and

Fig. 5 is a longitudinal section similar to Fig. 2, but showing a modified form of the improved Variable inductor.

In proceeding with a more detailed description reference will first be made to Figs. 1 to 4 inclusive, showing a variable inductor I0 which represents one practical embodiment 'of the invention. The improved inductor III .cor`nprises,l in general, an inductance coil means II, a core member I2 movable |into and out of the magnetic field of the coil means and an actuating device I3 for causing such movements of the core member. The improved variable inductor I 0 is here shown as including a base or support I 4 which may be a portion of the chassis of a radio apparatus, or the like, and comprises horizontal and vertical wall portions Ida and I 4b on which the inductance coil means II and the actuating device I3 are mounted, respectively.

The inductance coil means I I comprises a hollow inner coil or helix I5 and one or more outer coils or helixes I6 disposed in surrounding substantially coaxial relation to the inner coil. The inner and outer coils I5 and I6 can be in the rela.- tion of primary and secondary coils of an inductive coupling device or transformer. Although the inductance coil means II is here shown as including a plurality'of coils I5 and I6, it is not necessary thatV multiple coils be provided inas much as the inductance coil means may comprise a single coil or helix yor may comprise an auto transformer having coil sections inductively coupled by mutual inductance.

The inductance coil means II can be suitably mounted on the horizontal wall portion Ida of the base I4 as by means of a bracket I8 having spaced #upright parallel arms I8a and I8b. An insulating sleeve I 9 supported on the bracket arms I 8a and I8b and spanning the space therebetween forms a support for the coils I 5 and I6. The inner coil I 5 is here shown as being located inside the insulating sleeve I9 and the outer coil IB in surrounding relation to the sleeve such that this sleeve also forms an insulation between the respective coils.

The inner coil I5 has end portions projecting outwardly therefrom and forming a. pair of leads or terminals 20 and 2| to which further reference will be made hereinafter. Similarly, the outer coil I6 has projecting end portions 22 and 23 forming another such pair of leads or terminals.

The movable core member I2 is disposed in substantially coaxial relation to the inductance coil` means II and is axially movable into and out of the magnetic field of the latter. This core member can be a hollow core member movable into external surrounding relation to the coil means II but, preferably and as here shown, is movable into the magnetic field of the coil means'by movement into the coil means internally thereof. The corev member I2 accordingly comprises an axial stem portion -I2|a carried by a plunger portion I2b and disposed-substantially in coaxial alignment with the coil means II for movement of the stem portion 12o'. into the latter.

The core member I2, or at least the stem portion I2U. thereof, comprises a. metal body which can be from either a non-ferrous metal su'ch as copper or aluminum, or from a ferrous metal such as iron, but is preferably formed from a composition comprising finely divided iron, such as carbonyl iron and a binder such as a polyvinyl resin or other suitable plastic. When the core member l2 is made from such a composition of carbonyl iron and a binder it can be readily molded to the desired shape and during use thereof the finely divided iron produces the effect of a laminated core member.

As shown in Fig. 2, the 'core member I2 is also provided on the stem portion 12a thereof with an insulating cover 24 which isolates the stem portion I2a from metallic contact with the inner coil I5 when the stem portion is moved into the latter. The covering 24 can be of any suitable insulating or dielectric material such as polystyrene, or other suitable plastic, and can be molded in place on the stem portion I2a in surrounding relation thereto.

The actuating device I3 constitutes an important part of the improved inductor Ill and converts rotary actuating movement into the rectilinear axial movement by which the stem portion I2a of the core member I2 is moved into or out of the magnetic field of the inductance coil means II. The actuating device I3 comprises a pair of nested fixed and rotatable metal sleeves 26 and 21, of which the rotatable sleeve 21 is the inner sleeve and is supported for its rotation by the fixed or outer sleeve 25. The nested sleeves 26 and 21 are substantially coextensive and are disposed in an aligned substantially coaxial relation tothe inductance coil means II.

As shown in Fig. 2 the outer sleeve 2B is provided with an axial slot 28 formed in the wall thereof and having a length at least equal to the axial length of the coilmeans II. sleeve 21 is provided with a helical slot 29 formed in the wall thereof and extending in crossing rela-tion to the axial slot 28. A follower means, which in this instance is in the form of a pin 30, engages in or extends through both of these slots at their point of crossing relation and is connected with the plunger portion I2b of the core member I2. The pin 30 can be connected with the plunger portion I2b by having a press fit in a radial opening 3l such that the outer 5' end of the pin forms a projection on the plunger portion which constitutes the follower means for the slots.

The plunger portion I2b of the core member i2 is of substantially cylindrical shape and is axially slidable in the cylindrical, chamber 32 of the inner sleeve 21. During rotation of the inner sleeve in the outer .sleevex the point of crossing relation o-f the slots 2e and 29 moves longitudinally of the device along the axial slot causing the edge portions of the helical slot to exert a wedging action on the pin 30 to propel the core member I2 along the chamber 32 in one direction or the other depending upon the direction of the rotation of the inner sleeve. During such longitudinal movement of the core member l2 the engagement of the pin 3|) in the axial slot 28 holds the plunger portion |212 from rotating in the chamber 32 and thus-enables the The inner helical slot to be effective on the pin for propelling the core member.

The helical slot 29 can be a slot which has a uniform slope angle for all portions of its length or, if desired, may comprise slot portions having different slope angles which Will provide different rates of axial movement for the core member I2 in response to the rotary movement of the inner sleeve 21. Likewise, if desired, the helical slot 29 can be of a greater or shorter length than the 360 degrees of angular extent shown in Fig. 4.

As shown in Fig. 2, the outer and inner sleeves 26 and 21 are provided at the outer end thereof with transverse end walls 26a and 21a which are in engagement with each other when the inner sleeve is assembled into the outer sleeve. The inner sleeve can be retained in such assembled relation as by means of a snap ring 33 engaging in an internal annular groove 34 provided in the outer sleeve adjacent the inner end theren of.

For mounting the actuating device I3 on the wall portion I4b of the support I4, the outer sleeve 26 is provided With an externally threaded hollow stem 36 which extends through an opening 31 and is engaged by a clamping nut 3B. The inner sleeve 21 is provided at the outer end thereof with `an axial shaft portion 39 which extends through and is journaled in the threaded hollow stem portion 31 of the outer sleeve. The actuating device I3 is electrically isolated from the wall portion leb of the support by means of an insulating bushing 40 disposed between the outer sleeve 2B and such wall portion, and also by an insulating washer 4I disposed between the wall Mb and the clamping nut 38.

Rotary movement is adapted to be imparted to the inner sleeve 21 by suitable actuating means such as'the manually operable knob 42 shown in this instance. The knob 42 is mounted on the shaft portion 39 as by means of the transverse pin 43.

The position of the core member I2 relative to the inductance coil means II or, in other words, the inductance value setting of the device can be visibly indicated by a pointer which is movable with a knob 42 in relation to the graduations of a reference scale 45. The scale it is here shown as being a circumferentially extending scale disposed in surrounding relation to the shaft portion 39 and carried Vby a disk LS which is held in place against the insulating washer 4I by the nut 38.

From the construction just desclibed above it will now'be'seen that the cooperating slot and follower means of the variable inductor It! provides for the conversion of a rotary actuating movement yinto a rectilinear axial movement for the core member by which such core member can be moved into or out of the magnetic held of an inductance coil means by very accurate increments of such movement. It will also be seen that this rotary actuating movement for the core member also permits the use of an arcuate reference scale which can extend for a full 36o degrees or more around the axis of the rotary actuating movement and this permits the uations of the scale to be relatively Widely spaced apart for easier and more accurate reading thereof. i

- Additionally it will be understood that since the core lnflernberlzzin its retracted position is accesos housed in the metaly sleeves 2t and 21-it'wil1 be substantially fully shielded thereby.v Likewise it will be seen that the insulating coveringl on the stem portion of the core member I 2 permits this stem portion to be moved into the inner coil I5 in relatively close relation to theV convolutions thereof without coming into metallic contact therewith. i

As illustrating one manner of using the improved variable inductor I0, Fig. 2 shows byway of example certain conventional radiov circuit connections applied to this' device. These circuit connections include a signal lead wire 48 by which the terminal 20 of the inner coil I5 is connected with the grid 49 of an electron tube 50 of a radio apparatus, or the like.. These circuit rconnections also include a signal lead wire 5I by which the terminal 22 of the outer coil I6 `is connected with an antenne. 52. The circuit connections here shown also include conductor means 53 by which the terminals 2| and 23 of the coils I5 and I6 are connected with a ground 54. A conductor 55 is also provided which connects an intermediate point ofthe outer sleeve 26 with the ground 54.

Fig. 5 of the drawings shows a modined form of Variable inductor 51 which is of a construction generally similar to the variable inductor IIJ and in which the same corresponding parts are designated by the same reference characters. In

this modified variable inductor, however, the` stem portion 58 of the core member 59 is formed by a plurality of connected axially aligned sections 58a, 58h and 58e made of dilferent materials. for the core sections 58a, 58h and 58c depending' upon the inductance values desired to be produced by movement of these respective core sections into the magnetic field of the inductance coil means II. 58a is made of a ferrous metal such as iron, or a composition of carbonyl iron and a binder such as polyvinyl resin or the like, 'I'he core section 58h is here shown as being made of a non-metal lic insulating material, such as polystyrene or other suitable plastic. The core section 58e is here shown as being made of a non-ferrous metal, such as copper or aluminum.

The core sections 58a, 58h and 58o are all connected together in iixed relation so as to constitute the stem portion 58 which is carried by the plunger portion 59a of the core member 59. If desired, the core section 58a can be an integral portion of the plunger portion 59a in which case this plunger portion is made of the same material as the core section 58a. The core sections 58h and 58e can be connected with each other and with the core section 58a by the adhesive character of the insulating material used to form the core section 58h and such an adhesive connection between these core sections can be produced during the molding of the core section 58h.

In this modified variable inductor 51 an insulating covering 60 is also provided for the stem portion 58 of the core member 59 and prevents the core sections 58a and 58e from coming into metallic contact with the inner coil I 6 of the coil means II when these core sections are moved into the latter. The insulating sleeve 60 can be formed of any suitable insulating material, such as polystyrene or other suitable plastic, and. can be molded in place in surrounding relationto the stem. This insulating sleeve also serves the purpose of an additional connecting means by which Various different materials can be used In this instance the core section the core sections 58a, 58h and 58e are connected together and maintained in axially aligned relation.

In the modified variable inductor 5l the actuating device I3 functions in the same general manner as has already been described above for the variable inductor I0, but is of such length that the helical slot 2S will provide the necessary extent of axial movement for the stem 58 to bring any desired one of the core sections 58a, 58h and 53o into a substantially centrally located position of the inductance coil means II. By the rotary movement of the actuating knob d2 the core sections 56e, 58h and 58acan be moved in succession into the inner coil I5 and can also be withdrawn in succession in the reverse order from such coil member.

'I'he core section 58o being a non-ferrous metal section will have a negative effect on the inductance value of the inductance coil means II. The core section 58h being a non-metallic section will have substantially no eiiect on the inductance value ofthe coil means II. The core section 58h being a ferrous metal section will have a positive effect on the inductance value of the coil means II. It will thus be seen that by movement of the core sections 58e, 58h and 58a in succession into the coil means II a wide varia.- tion can be produced in the inductance value of this -coil means. In its retracted position the core member 59 is substantially fully shielded by the metal sleeves 26 and 2'I.

From the foregoing description and the accompanying drawings it will now be readily understood that this invention provides novel variable inductance devices which are of a simple and economical construction but which will be very accurate and reliable in use. It will also be seen that these novel variable inductors possess numerous desirable characteristics and advantages including those already explained above. In addition, it will be seen that the simple construction of these variable inductors will enable the same to be made in a very small size for use in compact or miniature radio apparatus and will also render these inductors especially suitable for use in high-frequency radio apparatus.

Although the novel invention have been variable inductors of this illustrated and described herein to a somewhat detailed extent it will be understood, of course, that the invention is not to be regarded as being limited correspondingly in scope but includes all changes and modifications coming within the terms of the claims hereof.

Having thus described our invention, we claim:

l. In a variable inductance device of the kind having a hollow coil means and a core stem movable endwise into said coil means, a pair of outer and inner coaxially nested sleeves disposed in adjacent substantially coaxially aligned relation to said coil means xed supporting sleeve and the other sleeve is rotatably supported by the fixed sleeve, one of said sleeves having an axial slot in the wall thereof and the other sleeve having a helical slot in the wall thereof extending in crossing relation to said axial slot, a plunger axially slidable in the inner sleeve, said sleeves dening an axially extending chamber-.having an open inner end presented toward said coil means, said core stem having one end thereof connected with said plunger such that said core stem is carried and actuated by said plunger, and follower means and one of which sleeves is a ae'rspea connected with said plunger and engaging in both of said slots at their point of crossing relation for imparting the axial movement to said plunger and core stem in response to the rotary movement of the rotatable sleeve, the length of travel of said plunger in said inner sleeve and the location of said open inner end relative to coil means being such that movementJ oi said plunger in one direction projects said core stein from said chamber into said coil means substantially coaxially of the latter and movement of said plunger in the opposite direction retraets said core stem from said coil means into a housed position in said chamber.

2. A variable inductance device as deiined in claim l in which the helical slot of said other sleeve has a non-uniform slope angle characteristic.

3. A variable inductance device as defined in claim 1 in which the length of travel of said f plunger is such that said core stem is substantially completely retractible from said coil means iby said movement of the plunger in said opposite direction.

4. In a variable inductance device of the kind having a base and a hollow coil means mounted thereon and a core stem movable endwise into said ycoil means, said base having a supporting wall spaced from one end of said coil means and provided with an opening, a pair of outer and inner ooaxially nested sleeves disposed in substantially coaxially aligned relation to said coil means and located between said wail and coil means, said outer sleeve being a stationary supporting sleeve having a hollow axial stem projection and being mounted on said wall by having said hollow stem projection xed in said opening, said inner sleeve being an actuating sleeve rotatable in said outer sleeve and having an axial actuating stem extending through said hollow stem projection, one of said sleeves having an axial slot in the wall thereof and the other having a helical slot in the wall thereof and extending in crossing relation to said axial slot, said sleeves defining an axially extending chamber having an open inner end presented toward said coil means, said core stem having one end thereof connected with said plunger such that said core stem is carried and actuated by said plunger, and follower means connected with said plunger and engaging in both of said slots at their point of crossing relation for imparting the axial movement to said plunger and core stem in response to the rotary movement of said inner sleeve, the length of travel of said plunger in said inner sleeve and the location of said open inner end re1- ative to said coil means being such that movement of said plunger in one direction projects said core stem from said chamber `into said coil means substantially coaxially of the latter `and movement of said plunger in the opposite direction retracts said core stern from said coil means into a housed position in said chamber.

GEORGE E. MORTON. MAURICE F. BADDOUR..

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,750,149 Zamboni Mar. 11, 1930 2,144,353 Weis Jan. 17, 1939 2,226,822 Kirk Dec. 31, 1940 2,335,205 Zepp Nov. 23, 1943 2,379,457 Rieker July 3, 1945 2,450,192 Freeman Sept. 28, 1948 2,508,338 Schaper May 16, 1950 

